You can get plywood pretty smooth. My recurve forms are made of construction grade 3/4 " plywood (3 lams thick, so 2.25 inches thick in all), and they are just fine. Don't damage the back at all. I like plywood better than dimension lumber because it doesn't warp over time the way lumber often will. Just cut the forms with a jigsaw and then hit them with a smooth file. When bending the stave or laminations into the form, you can always put a very thin strip of hardwood between the stave and the form, to protect the back, the same way you use a strip across the belly fibers to protect them from lifting up.
As for the arc:
Make your form, for explanations sake we will say it's like mine: plywood, 6 inches deep. make it several inches longer than the bows you plan to make in it, because you want to cut out an arc but leave a solid chunk of material on the outboard side. This is for wedging the laminations into place.
Now, say you want a 3 inch recurve (I mean, you want the tip of the bow 3" from the straight part of the bow). Make a mark 3" down from the top of the form. Square it up to the top of the form, for reference.
Now, say you want the tip to travel across 3" to get to straight. Measure back (toward the handle of the bow) 3" from the square reference mark you just made. Square this down and make a mark at 3".
NOW...set the tip of your compass at the mark you just made, and align the tip of the pencil with the first mark. Swing the arc up to the top of the form. That is the shape of your recurve. You need to make the opening an inch wide or so, so move the tip of your pencil 1" away from the handle region, and swing the same arc again, parallel to the first.
No problem. IT's easier to do than to describe.
This is just an example, and I'm not exactly sure these are the numbers I used. But you see the thinking involved, and I think you can handle it no sweat.
Scott
